Reinsman Gentle Guide Bit. 4 1/2" cheeks, 5" mouth. 
 
"The Gentle Guide is a great starter bit or transition bit. The cheeks offer similar advantages to a full cheek snaffle, but is even more gentle. The wider cheeks disperse pressure across the face to encourage turns and flexion instead of a single point like the full cheek. The slight gag action makes this bit 'slower' than a traditional full cheek because it takes the mouthpiece longer to engage."